utils/terminal.py

# -*- coding: utf-8 -*-
# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Terminal utilities

This module handles terminal interaction including ANSI color codes.
"""

from __future__ import print_function


class Color(object):
    """Conditionally wraps text in ANSI color escape sequences."""

    BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = range(8)
    BOLD = -1
    COLOR_START = '\033[1;%dm'
    BOLD_START = '\033[1m'
    RESET = '\033[0m'


    def __init__(self, enabled):
      """Create a new Color object, optionally disabling color output.

      Args:
        enabled: True if color output should be enabled. If False then this
          class will not add color codes at all.
      """
      self._enabled = enabled


    def Start(self, color):
      """Returns a start color code.

      Args:
        color: Color to use, .e.g BLACK, RED, etc.

      Returns:
        If color is enabled, returns an ANSI sequence to start the given color,
        otherwise returns empty string
      """
      if self._enabled:
          return self.COLOR_START % (color + 30)
      return ''


    def Stop(self):
      """Returns a stop color code.

      Returns:
        If color is enabled, returns an ANSI color reset sequence, otherwise
        returns empty string
      """
      if self._enabled:
          return self.RESET
      return ''

    def Color(self, color, text):
      """Returns text with conditionally added color escape sequences.

      Keyword arguments:
        color: Text color -- one of the color constants defined in this class.
        text: The text to color.

      Returns:
        If self._enabled is False, returns the original text. If it's True,
        returns text with color escape sequences based on the value of color.
      """
      if not self._enabled:
          return text
      if color == self.BOLD:
          start = self.BOLD_START
      else:
          start = self.COLOR_START % (color + 30)
      return start + text + self.RESET